a first printhead substrate;

a second printhead substrate; and

at least one signal line shared between said first printhead substrate and said second printhead substrate,

wherein said first printhead substrate comprises:

a plurality of printing elements, each including an electrothermal transducer;

a selection circuit which selects, in accordance with an input control signal, a printing signal input via a signal line or a predetermined signal for driving said plurality of printing elements;

an input unit which inputs a driving signal for driving said plurality of printing elements;

a shift register which receives via the at least one shared signal line the printing signal, a selection signal for time-divisionally driving said plurality of printing elements, and the control signal; and

a latch circuit which latches the printing signal and the control signal input to said shift register,

wherein, in a case where a printing operation by driving said plurality of printing elements in accordance with the printing signal is suppressed, said selection circuit selects the predetermined signal, and drives said printing elements on the basis of the predetermined signal by a short pulse signal insufficient to print,

said latch circuit includes said selection circuit,

the control signal includes an at least 2 bit signal, and

one bit of the at least 2 bit signal is input as a dedicated control signal to said selection circuit exclusively for said second printhead substrate.